The present invention relates to image reproduction systems, and more particularly to a laser driver for an injection laser diode and method of operating a laser driver in a high resolution laser recorder.
Laser image recorders may use a semiconductor laser diode (referred to herein as an injection laser diode, "ILD") to reproduce an image on a photographic media. The image is typically provided to the recorder in the form of digital or analog data that is used to modulate the ILD output to expose the photographic media. Due to the nature of the data and image, the operation of the device is complex. For example, recording resolution may be on the order of 300 pixels per inch, yielding nearly eight million pixels for an eight inch by eleven inch image. The image may be reproduced in about a half a minute (over 264,000 ILD operations per second) and may have 256 shades of gray with eight bits per pixel to describe the shading. Laser image recorders find application in a variety of fields, such as reconnaissance, medical (e.g., X-ray image reproduction), satellite imagery, computer-generated graphics, and the like.
The image reproduction process involves numerous steps in which an error in one step may be magnified in the next, and one of the more vexing problems encountered throughout the process is that of the effect of temperature on ILD operation. While the present invention addresses several problems, it may be more clearly understood by considering the invention as it addresses the temperature problems at several steps.